High voltage silicon rectifier



June 8, 1965 c, sg 3,188,549

HIGH VOLTAGE SILICON RECTIFIER Filed June 20, 1962 IN VENTOR. (A/5747? 4. sc /04? JTTUX/VE/f United States Patent 3,188,549 HIGH VOLTAGE SILICON RECTIFIER Chester L. Schuler, Brooklyn, N.Y., assignor to General Instrument Corporation, Newark, N.J., a corporation of New Jersey Filed June 20, 1962, Ser. No. 204,003 14 Claims. (Cl. 321-27) This invention relates to rectifiers, and more particularly to high voltage silicon rectifiers.

A string of silicon diodes may be used in series for high voltage work. To help assure uniform voltage distribution, it is already known to employ resistors of high value in shunt across the rectifiers. Because difiiculty still may arise with transient voltages, it is known to employ capacitors in shunt with the resistors and diodes.

At high voltages such a string becomes cumbersome, and introduces corona difliculty. The general object of the present invention is to improve high voltage silicon rectifiers. More particular objects are to provide a high voltage silicon rectifier which is simple, sturdy, reliable, long-lived, and yet which may be maufactured at moderate cost.

A further object is to provide rectifier strings which are conveniently packaged in modules which are easily stacked in dilferent numbers to meet varied requirements.

To accomplish the foregoing general objects, and other more specific objects which will hereinafter appear, my invention resides in the high voltage silicon rectifier assembly, and the elements thereof and their relation one to another, as are hereinafter more particularly described in the following specification. The specification is accompanied by a drawing in which:

FIG. 1 is a perspective view showing one of the puckshaped modules;

FIG. 2 is a partially sectioned elevation of a stack of such modules provided with anticorona rings;

FIG. 3 shows a stacked assembly designed to replace a vacuum tube;

FIG. 4 is a section through a module, and the upper end of an adjacent module;

FIG. 5 is a horizontal section taken approximately in the plane of the line 5-5 of FIG. 4;

FIG. 6 shows the components of one unit of the string, drawn to larger scale, and in separated relation;

FIG. 7 is a plan view drawn to smaller scale, of a disc of insulation material used to form a helix; and

FIG. 8 is a fragmentary section taken in tangential direction approximately in the plane of the line 88 of FIG. 5, and drawn to enlarged scale.

Referring to the drawing, and more particularly to FIGS. 1, 4 and 5, the rectifier module comprises a hollow puck shaped insulation casing generally designated 12. This has a terminal 14 in one end, and a terminal 16 in the other end. It houses a relatively long string of silicon diodes 18. A resistor 20 and a capacitor 22 are connected in shunt with each diode 18. The resulting string may be initially straight but is coiled to form a helix received in the casing 12. The upper end of the string is electrically connected to the upper terminal 14, and the lower end is electrically connected to the lower terminal 16.

The capacitors 22 are preferably of the flat ceramic disc type. The diodes 18 and the resistors 20 are tiny cylinder-s with short leads extending generally perpendicular to the axis of the cylinder. These parts are shown to larger scale in FIG. 6, in which ceramic capacitor 22 has leads 24; resistor 20 has leads 26; and diode 18 has leads 28. The leads 26 are preferably a little longer than the leads 28, and the leads 24 are still longer. The three leads at one side are soldered together and to the adjacent three leads of the next unit, so that the diodes are connected electrically in series. The soldering operation is facilitated, and the structure is improved both mechanically and electrically by the provision of tiny metal cups 30. These may be standard eyelet bodies of a type used in eyeletting machines. The legs or leads of the components are inserted in the cups, preferably with the diode on one side and the resistor on the other side of the capacitor leads. The soldering operation solders the leads together and to the cup, with the solder confined in and filling the cup.

The resulting string is coiled with the capacitors 22 in somewhat overlapped relation at the inside of the coil, as is clearly shown in FIG. 5, and with the cups 30 in radial position at the outside of the coil. The resistors 20 and diodes 18 assume an approximately tangential relation, intermediate the capacitors 22 and the cups 30. The leads of the components are readily bendable, and therefore the string of components may be assembled and soldered as a straight line or open string, and thereafter may be bent to the fiat helical relation shown in the drawing.

The inserts 14 and 16 are internally threaded. The outer surface of insert 14 is knurled and secured in the end 32, as by means of an epoxy cement. The outer end of the insert is preferably flush with the flat face of the end 32, and similarly the insert 16 is knurled and is cemented flush with the flat face of the end 34 of the puck. The inserts are tubular, but the inner ends are closed by tabs 36 and 38. These may be secured by spot welding or soldering.

The puck itself is made of a cylindrical wall 40 cut from tubing, and two flat circular discs 32 and 34 cut from sheet material. The material is preferably a socalled paper phenolic, that is, a laminated material impregnated with a phenolic resin. The side wall and ends are secured together by means of an epoxy cement. The end 32 preferably has two holes 42 to facilitate filling the puck with a potting material.

For manufacture in larger quantities the casing may be simplified by molding the cylindrical Wall 40 and the bottom 34 out of a single integral body of molding material. The top 32 is separate, but it too may be molded, in which case the upper edge of cylinder 40 and the periphery of the top 32 may be matingly stepped to facilitate and strengthen their assembly.

A helix of insulating material is preferably disposed with its coils between the coils of the diode string. The helix is a flat helix made of sheet material, and is shown at 44 in FIG. 4. It is preferably made of sheet Mylar having a thickness of, say 0.010 inch.

For convenience the helix 44 is preferably built up of simple flat discs secured end to end. One such disc is shown in FIG. 7, this being an annular or washer-shaped piece stamped from sheet Mylar and severed along a radial line 46. Two such elements may be secured together with their ends somewhat overlapped, as shown at 48 in FIGS. 4 and 5. The fragmentary section shown in FIG. 8 is taken in a tangential direction and shows how the end 50 of one piece overlaps the end 52 of the next piece, these ends being adhered together by means of small pieces 54 and 56 of Mylar adhesive tape. Two such discs provide nearly two convolutions of the helix, which is adequate for the present unit.

In the specific case here shown the string has 34 diodes in series, and the same number of resistors and capacitors. The capacitors are rated at 1000 volts, and the resistors at 10 megohms. The puck has a diameter of 2%. inches and a height of one inch. It is rated at 20,000 volts and milliamperes. It will be understood that these quantitative values are given solely by way of illustration, and are not intended to be in limitation of the invention.

The casing is preferably filled with a suitable potting material, usually an epoxy material. It is filled through either of the holes 32. Either the Mylar helix or the potting material provides effective insulation, but it is preferred to use both as a precautionary matter, the Mylar helix serving to guard against any accidental displacement or contact between adjacent convolutions of the string prior to or during the potting operation.

The module is designed for high voltage assemblies, and therefore high voltage practices should be followed. For example, it is good practice to incorporate grading toroids between modules, and terminating toroids of larger diameter at the ends. FIG. 2 illustrates the use of such toroids, there being grading toroids 68 between successive pucks 62, and larger diameter toroids 64 at the ends. The large toroids may be made of two oppositely convexed pieces of sheet metal, and the smaller ones may be made of a single piece of sheet metal with a rolled peripheral edge. The stack is shown broken away at 66 to indicate that a larger number of'pucks may be used.

The pucks are held together by short threaded studs, as shown at 7% in FIG. 4, and similar studs at the ends receive nuts 72 (FIG. 2) which hold the toroids 64 in position, and which also receive leads 74. When toroids -ibe adequate, it being easy to add or remove modules. Further advantages are simplicity and convenience.

It will be apparent thatwhile I have shown and described the invention in a preferred form, changes may be made without departing from the scope of the invention, as sought to be defined in the following claims.

I claim:

1. A high voltage rectifier module comprising a hollow puck-shaped insulation casing having a terminal in each end, a relatively long string of silicon diodes, a resistor and a capacitor in shunt with each diode, said capacitors being of the fiat ceramic disc type, and being externally insulated, said diodes and resistors being tiny cylinders with short leads extending generally perpendicular to are not used it is good practice to cap the ends with small spheres or cap nuts to reduce the electrical stress. The stack also may be operated immersed in oil.

It is a simple matter to fit a vacuum tube type base to an assembly of modules, thus making possible a field replacement of a high voltage rectifier tube by means of a silicon rectifier. Referring to FIG. 3, there is a stack of a desired number of modules 76 terminating in a metal cap 78 at one end, dimensioned like a vacuum tube cap. A base $0 with prongs 82 dimensioned like a vacuum tube base is secured at the other end. Only one prong is actually employed for electrical connection, there being no need for a filament supply. The parts 78 and. 80 may be secured to threaded studs for electrical and mechanical connection to the stack, and the pucks are themselves secured together by threaded studs, as previously described.

Although I prefer to use internally threaded terminals at both ends of the puck, it will be understood that the puck may be given a male terminal at one end and a female terminal at the other end. a In such case the pucks are screwed together without the need for a separate threaded stud. At the ends of a stack of pucks one end has its male stud to receive a nut or/and anticorona hardware (or a vacuum tube part, as in FIG. 3). .The other end has a female terminal which is given a short threaded stud.

To make the puck-shaped modules shown in FIGS. 4 and 5, the inserts 14 and 16 are first cemented in the ends 32 and 34. The tube 4% is then cemented to the bottom 34. The components shown in FIG. 6 are assembled in metal cups to form a string of desired length. The string is bent to form the desired coil or helix. The lower end is soldered to the tab 33. The Mylar helix is put in position, which is readily done with a rotating motion. The upper end of the helix is soldered to the tab 3d, and the cover 32 is then cemented to the side wall 40. The epoxy potting mixture is later poured through one of the openings 42.

It is believed that the construction and method of use of my improved high voltage silicon rectifier, as well as the advantages thereof, will be apparent from the foregoing detailed descript-ion. The module is rugged and characterized by long life. It has good lL gh voltage geometry, and lends itself to even field distribution by means of simple and easily applied corona shields. The modules are easily stackable in any position. There is flexibility because an apparatus design change may be made in the event that final circuit tests indicate that a higher voltage is required, or that a lower voltage would the axis of the cylinder, tiny metal cups receiving the a six leads at the adjacent ends of successive units of the string, said six leads being soldered in said cup, the

resulting string being bendable but stiff enough to be initially self-supporting and being coiled to form a helix received in said casing with the capacitors in somewhat overlapped relation at the inside of thecoil and with the cups in radial position at the outside of the coil and with the resistors and diodes in approximately tangential relation intermediate the capacitors and the cups, the capacitors being overlapped in uniform sequence so that the adjacent faces have minimum potential difference, the

ends of the string being connected each to its adjacent terminal.

Z. A high voltage rectifier module comprising a hollow puck-shaped insulation casing having a terminal in each end, the casing being cylindrical with fiat parallel ends and the diameter being substantially greater than the height, a relatively long string of silicon diodes, a resistor and a capacitor in shunt with each diode, said capacitors being of the flat ceramic disc type and being externally insulated, said diodes and resistors being tiny cylinders with short leads extending generally perpendicular to the axis of the cylinder, tiny metal cups receiving the six leads at the adjacent ends of successive units of the string, said six leads being soldered in said cup, the resulting string being bendable but stiif enough to be initially self-supporting and being coiled to form a helix received in said casing with the capacitors in somewhat overlapped relation at the inside of the coil and with the cups in radial position at the outside of the coil and with the resistors and diodes in approximately tangential relation intermediate the capacitors and the cups, the capacitors being overlapped in uniform sequence so that the adjacent faces have minimum potential difference, the ends of the string being connected each to its adjacent terminal, a helixrof sheet insulating material disposed with its coils between the coils of the aforesaid string of diodes and resistors and capacitors, and solid potting material filling said casing around said string and insulation helix.

3. A high voltage rectifier module comprising a hollow puck-shaped insulation casing having a threaded metal insert in each end, at least one of said inserts being internally threaded, the outer end of the internally threaded insert being flush with the flat face of the end of the puck, a relatively long string of silicon diodes, a resistor and a capacitor in shunt with each diode, said capacitors being of the flat ceramic disc type, and being externally insulated, said diodes and resistors beingtiny cylinders with short leads extending generally perpendicular to the axis of the cylinder, tiny metal cups receiving the six leads at the adjacent ends of successive units of the string, said six leads being soldered in said cup, the resulting string being bendable but still enough to be initially self-supporting and being coiled to form a helix received in said casing with the capacitorsin somewhat overlapped relation at the inside of the coil and with the cups in radial position at the outside of the coil and with the resistors and diodes in approximately tangential relation intermediate the capacitors, and the cups, the

capacitors being overlapped in uniform sequence so that the adjacent faces have minimum potential diiference, the ends of the string being connected each to its adjacent insert.

4. A high voltage rectifier module comprising a hollow puck-shaped insulation casing having a threaded metal insert in each end, the casing being cylindrical with flat parallel ends and the diameter being substantially greater than the height, at least one of said inserts being internally threaded, the outer end of the internally threaded inser-t being flush with the fiat face of the end of the puck, a relatively long string of silicon diodes, a resistor and a capacitor in shunt with each diode, said capacitors being of the flat ceramic disc type, and being externally insulated, said diodes and resistors being tiny cylinders with short leads extending generally perpendicular to the axis of the cylinder, tiny metal cups receiving the six leads at the adjcaent ends of successive units of the string, said six lead-s being soldered in said cup, the resulting string being bendable but stiff enough to be initially self-supporting and being coiled to form a helix received in said casing with the capacitors in somewhat overlapped relation at the inside of the coil and with the cups in radial position at the outside of the coil and with the resistors and diodes in approximately tangential relation intermediate the capacitors and the cups, the capacitors being overlapped in uniform sequence so that the adjacent faces have minimum potential difference, the ends of the string being connected each to its adjacent insert, and a helix of sheet insulating material disposed with its coils between the coils of the aforesaid string of diodes and resistors and capacitors. 5. A high voltage rectifier module comprising a hollow puck-shaped insulation "casing having a threaded metal insert in each end, the casing being cylindrical with fiat parallel ends and the diameter being substantially greater than the height, at least one of said inserts being internally threaded, the outer end of the internally threaded insert being flush with the fiat face of the end of the puck, a relatively long string of silicon diodes, a resistor and a capacitor in shunt with each diode, said capacitors being of the fiat ceramic disc type, and being externally insulated, said diodes and resistors being tiny cylinders with short leads extending generally perpendicular to the axis of the cylinder, tiny metal cups receiving the six leads at the adjacent ends of successive units of the string, said six leads being soldered in said cup, the resulting string being bendable but stifi enough to be initially self-supporting and being coiled to form a helix received in said casing with the capacitors in somewhat overlapped relation at the inside of the coil and with the cups in radial position at the outside of the coil and with the resistors and diodes in approximately tangential relation intermediate the capacitors and the cups, the capacitors being overlapped in uniform sequence so that the adjacent faces have minimum potential difference, the ends of the string being connected each to its adjacent insert, and potting material filling said casing around said string and insulation helix.

6. A high voltage rectifier module comprising a hollow puck-shaped insulation casing having a threaded metal insert in each end, at least one of said inserts being internally threaded, the outer end of the internally threaded insert being flush with the flat face of the end of the puck, a relatively long string of silicon diodes, a resistor and a capacitor in shunt with each diode, said capacitors being of the flat ceramic disc type, and being externally insulated, said diodes and resistors being tiny cylinders with short leads extending generally perpendicular to the axis of the cylinder, tiny metal cups receiving the six leads at the adjacent ends of successive units of the string, said six leads being soldered in said cup, the resulting string being bendable but stiff enough to be initially self-supporting and being coiled to form a helix received in said casing with the capacitors in somewhat overlapped relation at the inside of the coil and with the cups in radial position at the outside of the coil and with the resistors and diodes in approximately tangential relation intermediate the capacitors and the cups, the capacitors being overlapped in uniform sequence so that the adjacent faces have minimum potential difference, the ends of the string being connected each to its adjacent insert, a helix of sheet Mylar insulating material disposed with its-coils between the coils of the aforesaid string of diodes, and resistors and capacitors, and an epoxy potting material filling said casing around said string and insulation helix.

7. A high voltage rectifier comprising a stack of puckshaped'modules, each as defined in claim 3, each module being physically and electrically connected to an adjacent module by means of a short threaded stud screwed into an adjacent internally threaded insert, the outer ends of the end modules having threaded studs receiving nuts for holding terminal wires and anticorona hardware.

8. A high voltagerectifier comprising a stack of puckshaped modules, each as defined in claim 3, a plurality of small metal toroids disposed between said pucks, the diameter of said toroids being larger than that of the pucks, and a larger diameter toroid at each end of the stack, said modules and toroids being held together by means of a short threaded stud received in an adjacent internally threaded insert, and nuts at the ends.

9. A high voltage rectifier designed to readily replace a vacuum tube rectifier in a chassis having a vacuum tube socket for receivingthe rectifier, said rectifier comprising a stack of modules, each as defined in claim 3, said modules being physically and electrically connected together by means of a short threaded stud received in the insert of an adjacent module, additional studs at the ends of the stack, a metal cap dimensioned like a vacuum tube cap secured on the stud at one end, and a pronged base dimensioned like a vacuum tube base secured to the stud at the other end of the stack.

10. A high voltage rectifier module comprising a hollow puck-shaped insulation casing having a terminal in each end, the casing being cylindrical with flat parallel ends and the diameter being substantially greater than the height, a relatively long string of silicon diodes, a resistor and a capacitor in shunt with each diode, said capacitors being of the flat disc type, and externally insulated, said diodes and resistors being tiny cylinders with short leads extending generally perpendicular to the axis of the cylinder, there being six collateral leads sol dered together at the adjacent ends of succesive units of the string, the resulting string being bendable but stiff enough to be initially self-supporting and being coiled to form a self-supporting helix received in said casing with the capacitors in somewhat overlapped relation at the inside of the coil and with the resistors and diodes in approximately tangential relation, the capacitors being overlapped in uniform sequence so that the adjacent faces have minimum potential difference, the ends of the string being connected each to its adjacent terminal.

11. A high voltage rectifier module comprising a hollow puck-shaped insulation casing having a terminal in each end, the casing being cylindrical with flat parallel ends and the diameter being substantially greater than the height, a relatively long string of silicon diodes, a resistor and a capacitor in shunt with each diode, said capacitors being of the fiat disc type and externally insulated, said diodes and resistors being tiny cylinders with short leads extending generally perpendicular to the axis of the cylinder, there being six collateral leads soldered together at the adjacent ends of successive units of the string, the soldered bunch of leads extending horizontally in divergent relation, the resulting string being coiled to form a self-supporting helix received in saidv casing with the capacitors disposed substantially horizontally in somewhat overlapped relation at the inside of the coil and with the leads in radial position at the outside 7 r of the coil and with the resistors and diodes in approximately tangential relation intermediate the capacitors and the leads, the capacitors being overlapped in uniform sequence so that the adjacent faces have minimum potential difference, the ends of the string being connected each toits adjacent terminal.

12. A high voltage rectifier comprising a stack of puckshaped modules, each module comprising a hollow puckshaped insulation casing having a threaded metal insert in each end, the casing being cylindrical with flat parallel ends and the diameter being substantially greater than the height, at least one of said inserts being internally threaded, the outer end of the internally threaded insert being flush with the fiat face of the end of the puck, a string of silicon diodes, a resistor and a capacitor in shunt with each diode, said string being coiled to form a selfsupporting helix received in said casing, the ends of the string being connected each to its adjacent insert, each module being physically and electrically connected to an adjacent module by means of a short threaded stud screwed into an adjacent internally threaded insert.

13. A high voltage rectifier comprising a stack of puckshaped modules, each module comprising a hollow puckshaped insulation casing having a threaded metal insert in each end, the casing being cylindrical with flat parallel ends and the diameter being substantially greater than the height, at least one of said inserts being internally threaded, the outer end of the internally threaded insert being flush with the flat face of the end of the puck, a string of silicon diodes, a resistor, and a capacitor in shunt with each diode, said string being coiled to form a selfsupporting helix received in said casing, the ends of the string being connected each to its adjacent insert, a plurality of small metal toroids disposed between said pucks, the diameter of said toroids being larger than that of the pucks, and a larger diameter toroid at each end of the stack, said modules and toroids being held together by means of a short threaded stud received in an adjacent internally threaded insert, and nuts at the ends.

14. A high voltage rectifier designed to readily replace a vacuum tube rectifier in a chassis having a vacuum tube socket for receiving the rectifier, said rectifier comprising a stack of puck-shaped modules, each module comprising a hollow puck-shaped insulation casing having a threaded metal insert in each end, the casing being cylindrical with flat parallel ends and the diameter being substantially greater than the height, at least one of said inserts being internally threaded, the outer end of the internally threaded insert being flush with the flat face of the end of the puck, a string of silicon diodes, a resistor and a capacitor in shunt with each diode, said string being coiled to form a self-supporting helix received in said casing, the ends of the string being connected each to its adjacent insert, said modules being physically and electrically connected together by means of a short threaded stud received in the insert of an adjacent module, additional studs at the ends of the stack, a metal cap dimensioned like a vacuum tube cap secured on the stud at one end, and a pronged base dimensioned like a vacuum tube base secured to the stud at the other end of the stack.

References (Iited by the Examiner UNITED STATES PATENTS 1,723,579 8/29 Ruben 3l7-2 34 2,562,048 7/51 Lamm et al 317-234 2,752,537 6/56 Wolfe 317-101 2,984,773 5/61 Guldemond et a1 317-234 3,059,165 10/62 Meykar 321-44 3,159,769 7 12/64 Parrish 317-101 LLOYD MCCOLLUM, Primary Examiner. ROBERT L. SIMS, Examiner. 

6. A HIGH VOLTAGE RECTIFIER MODULE COMPRISING A HOLLOW PUCK-SHAPED INSULATION CASING HAVING A THREADED METAL INSERT IN EACH END, AT LEAST ONE OF SAID INSERTS BEING INTERNALLY THREADED, THE OUTER END OF THE INTERNALLY THREADED INSERT BEING FLUSH WITH THE FLAT FACE OF THE END OF THE PUCK, A RELATIVELY LONG STRING OF SILICON DIODES, A RESISTOR AND A CAPACITOR IN SHUNT WITH EACH DIODE, SAID CAPACITORS BEING IN THE FLAT CERAMIC DISC TYPE, AND BEING EXTERNALLY INSULATED, SAID DIODES AND RESISTORS BEING TINY CYLINDERS WITH SHORT LEADS EXTENDING GENERALLY PERPENDICULAR TO THE AXIS OF THE CYLINDER, TINY METAL CUPS RECEIVING THE SIX LEADS AT THE ADJACENT ENDS OF SUCCESSIVE UNITS OF THE STRING, SAID SIX LEADS BEING SOLDERED IN SAID CUP, THE RESULTING STRING BEING BENDABLE BUT STIFF ENOUGH TO BE INITIALLY SELF-SUPPORTING AND BEING COILED TO FORM A HELIX RECEIVED IN SAID CASING WITH THE CAPACITORS IN SOMEWHAT OVERLAPPED RELATION AT THE INSIDE OF THE COIL AND WITH THE CUPS IN RADIAL POSITION AT THE OUTSIDE OF THE COIL AND WITH THE RESISTORS AND DIODES IN APPROXIMATELY TANGENTIAL RELATION INTERMEDIATE THE CAPACITORS AND THE CUPS, THE CAPACITORS BEING OVERLAPPED IN UNIFORM SEQUENCE SO THAT THE ADJACENT FACES HAVE MINIMUM POTENTIAL DIFFERENCE, THE ENDS OF THE STRING BEING CONNECTED EACH TO ITS ADJACENT INSERT, A HELIX OF SHEET MYLAR INSULATING MATERIAL DISPOSED WITH ITS COILS BETWEEN THE COILS OF THE AFORESAID STRING OF DIOSES, AND RESISTORS AND CAPACITORS, AND AN EPOXY POTTING MATERIAL FILLING SAID CASING AROUND SAID STRING AND INSULATION HELIX. 